Nowadays, the potential of phase change process in liquids at micro scale attracts the scientists to fabricate this type of micropumps. Such micropumps have widely found applications in industrial and medical equipments such as recent printers. Not using mechanical parts such as valves, and having small sizes and high and controllable mass flow rates are the advantages of these micropumps. In the nozzle diffuser phase change micropump a heat pulse generates a bubble in a chamber; therefore, the pressure pulse which is generated by the bubble, causes the bubble to expand suddenly with high rate, then the pressure of bubble reduces to the vapor pressure and causes negative rate of expansion to the bubble. After the bubble reaches its maximum size, the bubble collapses and disappears. Due to the existence of difference in pressure drop in the nozzle and diffuser sections, one can see unidirectional flow through diffuser direction. The objective of this article is to analyze theoretically the thermo-hydrodynamic behavior of the Isopropyl Alcohol (IPA) bubble of a phase change micropump. Considering the simultaneous effects of hydrodynamic and thermal characteristics of the bubble in the bubble creation chamber, and temperature-saturation pressure relation of the IPA bubble based on Clausius-Clapeyron equation, the dynamics of the embedded bubble has been modeled. Applying the results of the bubble dynamics, the flow rate of the micropump for one cycle of operation has been attained. The obtained theoretical values for the micropump flow rate show good agreement with the corresponding existing experimental data.

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